The present invention refers to the technical field of extraoral dental radiography, and particularly to a apparatus alternatively performing panoramic radiographies, cranial teleradiographies and optionally cone beam volumetric radiographies of facial skeleton. All these types of radiographies are well known in the art.
Panoramic radiography (also known as orthopantomography) produces a radiographic image of a curved plan approximating patient jaws, with blurring of the anatomical structures laying outside a narrow layer around the predesigned curved plane. This kind of acquisition is also indicated in the following with PAN.
Teleradiography is a projective radiographic technique, producing radiographic images of the skull or of other anatomical areas from different projections, with minimum magnification and geometrical distortion. Usually two perspectives are represented, latero-lateral and antero-posterior.
Cone beam volumetric radiography (also known as CBCT) is the acquisition, from different projection angles, of a series of two-dimensional radiographic images which will be processed post-acquisition to reconstruct three-dimensional volumes.
It is well known in the art that the positions of PAN, CBCT and teleradiographic sensors, and therefore the distance of the specific sensor from the X-ray source, are opportunely chosen so as to get the best radiographic result. The distance between X-ray source and X-ray sensor varies according to the kind of sensor. Generally speaking, the distance between teleradiographic sensor and X-ray source is the largest, while the distance between PAN sensor and X-ray source is smaller than the distance between CBCT sensor and X-ray source.
Indicatively, the distances allowing to get optimal radiographic results are the following:                X-ray source—PAN sensor distance: 520-580 mm;        X-ray source—CBCT sensor distance: 600-700 mm;        X-ray source—teleradiographic sensor distance: 1400-1600 mm.        
Radiographic apparatuses acquiring panoramic and teleradiographic radiographies have been on the market for over 50 years. This kind of apparatuses generally has a C-arc, at whose ends the X-ray source and the X-ray detector are positioned at an appropriate distance to acquire panoramic images.
When a teleradiographic acquisition has to be performed, the X-ray detector must be positioned at a greater distance from the X-ray source than allowed by the dimension of the C arc. For this reason, such apparatuses are provided with a supplementary arm supporting the X-ray detector at an appropriate distance for performing teleradiography.
Traditionally, such apparatuses are provided with an X-ray source and at least one X-ray detector. When only one detector is present, this must be manually or automatically relocated in the desired position for panoramic or teleradiographic acquisition. When more than one detector is present, means for removing obstacles along the X-ray path between the X-ray source and X-ray detector for the specific acquisition are also present. One of the many examples of such apparatuses is Vatech's patent application WO200718332.
This kind of apparatus shows many drawbacks.
The first drawback lies in the high cost of X-ray detectors, which nowadays cost four-ten times the price of an X-ray source.
The second drawback, tightly linked to the first, lies in the fact that in the apparatuses provided with one X-ray detector only, which has to be manually relocated to perform the desired acquisition, there is a great risk of breakage, in that the X-ray detector is delicate and can undergo dangerous accidental falls during relocation. Moreover, in the apparatus removable connection systems must be provided, which must be safe under the point of view of electric transmission and reliable in the repeatability of positioning.
The third drawback lies in the fact that, due to acquisition geometry, on the same apparatus two different suitable patient positioning systems must be present, one for PAN/CBCT and one for teleradiography, with ensuing cost increase.
When during the same session a panoramic and a teleradiographic acquisition must be performed on the same patient (for instance an orthodontic patient), first the panoramic acquisition must be performed, then: in the simpler case of two X-ray detectors, the patient has to be moved from the first to the second patient positioning system; in the more complicate case of one X-ray detector only, the patient must be moved from the first to the second patient positioning system and the X-ray detector must be relocated. This leads to a significant prolonging of acquisition time for both operator and patient.